@define-mixin image-2x $image, $width, $height
{
    @media (min--moz-device-pixel-ratio: 1.3),
           (-o-min-device-pixel-ratio: 2.6/2),
           (-webkit-min-device-pixel-ratio: 1.3),
           (min-device-pixel-ratio: 1.3),
           (min-resolution: 1.3dppx)
    {
        background-image: url($image);
        background-size: $width $height;
    }
}